Parameter value filtering should allow selection of already filtered elements only.

[DillonJ]

Say I filter the parameter value pane by a parameter_name that can only have true or false as values, if I then go to filter by parameter value, a user would expect to see a list of only the parameter values in the currently filtered list - in this case, only true or false. Instead, the user sees every parameter value.

Generally speaking, I believe the behaviour a user would expect is that the items available to filter by should be from the currently filtered list, and not the unfiltered list.